AperTO - Archivio Istituzionale Open Access dell'Università di Torino
Original Citation:
Enhancement by anthraquinone-2-sulphonate of the photonitration of phenol by nitrite: Implication for the photoproduction of nitrogen dioxide by coloured dissolved organic matter in surface waters.
Published version:
DOI:10.1016/j.chemosphere.2010.09.025 Terms of use:
Open Access
(Article begins on next page)
Anyone can freely access the full text of works made available as "Open Access". Works made available under a Creative Commons license can be used according to the terms and conditions of said license. Use of all other works requires consent of the right holder (author or publisher) if not exempted from copyright protection by the applicable law. Availability:
This is the author's manuscript
This Accepted Author Manuscript (AAM) is copyrighted and published by Elsevier. It is posted here by agreement between Elsevier and the University of Turin. Changes resulting from the publishing process - such as editing, corrections, structural formatting, and other quality control mechanisms - may not be reflected in this version of the text. The definitive version of the text was subsequently published in P. R. Maddigapu, C. Minero, V. Maurino, D. Vione, M. Brigante, G. Mailhot. Enhancement by Anthraquinone-2-sulphonate of the Photonitration of Phenol by Nitrite: Implications for the Photoproduction of Nitrogen Dioxide by Coloured Dissolved Organic Matter in Surface Waters. Chemosphere 2010, 81, 1401-1406.
DOI: 10.1016/j.chemosphere.2010.09.025.
You may download, copy and otherwise use the AAM for non-commercial purposes provided that your license is limited by the following restrictions:
(1) You may use this AAM for non-commercial purposes only under the terms of the CC-BY-NC-ND license.
(2) The integrity of the work and identification of the author, copyright owner, and publisher must be preserved in any copy.
(3) You must attribute this AAM in the following format:
P. R. Maddigapu, C. Minero, V. Maurino, D. Vione, M. Brigante, G. Mailhot. Enhancement by Anthraquinone-2-sulphonate of the Photonitration of Phenol by Nitrite: Implications for the Photoproduction of Nitrogen Dioxide by Coloured Dissolved Organic Matter in Surface Waters. Chemosphere 2010, 81, 1401-1406.
ENHANCEMENT BY ANTHRAQUINONE-2-SULPHONATE OF THE PHOTONITRATION OF PHENOL BY NITRITE: IMPLICATIONS FOR THE PHOTOPRODUCTION OF NITROGEN DIOXIDE BY COLOURED DISSOLVED ORGANIC MATTER IN SURFACE WATERS
Pratap Reddy Maddigapu,a Claudio Minero,a Valter Maurino,a Davide Vione,a,b,* Marcello Brigante,c,* Gilles Mailhot,c
a
Dipartimento di Chimica Analitica, Università di Torino, Via P. Giuria 5, 10125 Torino, Italy. http://www.chimicadellambiente.unito.it
b
Centro Interdipartimentale NatRisk, Università degli Studi di Torino, Via Leonardo da Vinci 44, 10095 Grugliasco (TO), Italy.
c
Laboratoire de Photochimie Moléculaire et Macromoléculaire (LPMM), Université Blaise Pascal, UMR CNRS 6505, F-63177, Aubière Cedex, France.
* Address correspondence to either author. E-mail: davide.vione@unito.it (D.V.); marcello.brigante@univ-bpclermont.fr (M.B.).
Abstract
Anthraquinone-2-sulphonate (AQ2S) under UVA irradiation is able to oxidise nitrite to •NO2 and to induce the nitration of phenol. The process involves the very fast reactions of the excited triplet state 3AQ2S* and its 520-nm absorbing exciplex with water, at different time scales (ns and µs, respectively). Quinones are ubiquitous components of coloured dissolved organic matter (CDOM) in surface waters and AQ2S was adopted here as a proxy of CDOM. Using a recently developed model of surface-water photochemistry, we found that the oxidation of nitrite to •NO2 by 3CDOM* could be an important •NO2 source in water bodies with high [NO2−] to [NO3−] ratio, for elevated values of column depth and NPOC.
Keywords: aromatic photonitration; photosensitised processes; nitroaromatic compounds; nitrophenols; nitrogen dioxide.
Introduction
Nitrophenols are environmentally harmful nitroaromatic compounds, with a potential to act as uncoupling agents in oxidative phosphorylation (Shea et al., 1983) and to cause oxidative damage to DNA (Chiron et al., 2007a). Nitrophenols occur in surface waters because of several pathways: atmospheric deposition, hydrolysis of parathion and similar products (Agarwal et al., 1994), and
photonitration of the corresponding phenols (Chiron et al., 2007b). The latter may be environmental transformation intermediates of phenolic herbicides (Chiron et al., 2009). Exposure to nitrophenols can cause harmful effects to algae (Umamaheswari and Venkateswarlu, 2004) and aquatic organisms (Howe et al., 1994).
The photonitration of aromatic compounds is started by the production of •NO2 upon photolysis of nitrate and nitrite (Machado and Boule, 1995; Dzengel et al., 1999; Vione et al., 2002). Another potentially important source of •NO2 in the aqueous solution is the photooxidation of nitrite, in the presence of •OH or of irradiated metal oxides (Chiron et al., 2007b).
The excited triplet states of coloured dissolved organic matter (3CDOM*) are important reactive transients in surface waters (Halladja et al., 2007). The species 3CDOM* are often able to abstract electrons or hydrogen atoms from other dissolved molecules, as well as to transform ground-state O2 into 1O2. 3CDOM* is for instance involved to a very significant extent into the transformation of phenylurea herbicides (Canonica et al., 2006). The excited triplet states of quinones are representative of the coloured moieties of natural dissolved organic matter (Cory et al., 2005). They have often very high reduction potentials (Wardman, 1989) and could oxidise nitrite to •NO2 (E°•NO2/NO2−≈ 1 V). However, no data are available on the process of •NO2 production by nitrite and 3
CDOM*, nor on the potential of such a reaction to induce aromatic nitration.
We chose anthraquinone-2-sulphonate (AQ2S) as model photoactive organic compound. The photochemistry and photophysics of AQ2S are rather well known (Loeff et al., 1983; Maurino et al., 2008). Interestingly, the excited triplet state of AQ2S (3AQ2S*) does not react with O2 to yield 1
O2 (Maddigapu et al., 2010). With AQ2S it is thus possible to study the triplet-state reactivity, without the additional complication of the reactions of 1O2.
The nitration of phenol was studied upon irradiation of AQ2S and nitrite, to get insight into the ability of the process to yield harmful nitroaromatic compounds. Moreover, the transformation of phenol into nitrophenols is a suitable probe reaction for the assessment of •NO2 generation (Chiron et al., 2007b). The potential importance of the production of •NO2 by triplet state reactivity under environmental conditions was assessed by means of a combination of experimental results and modelling of surface-water photochemistry.
Experimental
All reagents were of analytical grade and were used as received, without further purification. Water used was of Milli-Q quality.
Irradiation experiments. The aqueous solutions to be irradiated (5 mL total volume) were placed
into cylindrical Pyrex glass cells (4.0 cm diameter, 2.3 cm height, lateral inlet with screw-cap closure). Irradiation with magnetic stirring took place under a 40 W Philips TL K05 UVA lamp. The incident photon flux in solution, actinometrically determined with the ferrioxalate method
(Kuhn et al., 2004) was 2.1⋅10−5 Einstein L−1 s−1 and corresponded to a UV irradiance (290-400 nm) of 28 W m−2, measured with a CO.FO.ME.GRA. (Milan, Italy) power meter. Figure 1 reports the emission spectrum of the adopted lamp, measured with an Ocean Optics SD 2000 CCD spectrophotometer and normalised to the actinometry results, taking into account the transmittance of the Pyrex glass window of the irradiation cells. The Figure also reports the absorption spectra of AQ2S and nitrite, taken with a Varian Cary 100 Scan UV-Vis spectrophotometer.
Analytical determinations. After irradiation the solutions were allowed to cool for 10-15 min
under refrigeration, and then analysed by High Performance Liquid Chromatography coupled with UV-Vis detection (HPLC-UV). The adopted Merck-Hitachi instrument was equipped with AS2000A autosampler (100 µL sample volume), L-6200 and L-6000 pumps for high-pressure gradients, Merck LiChrocart RP-C18 column packed with LiChrospher 100 RP-18 (125 mm × 4.6 mm × 5 µm), and L-4200 UV-Vis detector (detection wavelength 210 nm). The isocratic elution was carried out with a 50:50 mixture of methanol: aqueous H3PO4 (pH 2.8). With an eluent flow rate of 1.0 mL min−1 the retention times were (min): phenol (2.55), 4-nitrophenol (3.20), 2-nitrophenol (5.15). The column dead time was 0.90 min.
Kinetic treatment of the data. The time evolution data of phenol were fitted with pseudo-first
order equations of the form Ct =Co exp(−kdPh⋅t), where Ct is the concentration of phenol at the time t, Co its initial concentration, and kdPh the pseudo-first order degradation rate constant. The initial transformation rate of phenol is RatePh = kdPh Co. The time evolution of 2- and 4-nitrophenol was fitted with C k C (k k ) 1 [exp( k t) exp( kdNP t)]
Ph d Ph d NP d o NP f t′= ⋅ ⋅ − ⋅ − ⋅ − − ⋅ − , where C’t is the concentration of each nitrophenol at the time t and kfNP and kdNP are the pseudo-first order formation and transformation rate constants of each nitrophenol. Co and kdPh have the same meaning as before. The nitrophenol initial formation rate is RateNP = kfNP Co. The reported errors on the rates were derived at the σ level from the fit of the experimental data (intra-series variability). The reproducibility of repeated runs (inter-series variability) was in the range of 10-15%.
Radiation absorption calculations. To calculate the photon flux absorbed by AQ2S (PaAQ2S) in the presence of nitrite, one should consider that nitrite and AQ2S compete for the lamp irradiance (see Figure 1). The absorbance of a species S does not vary if S is alone in solution or if it is in mixture with other radiation-absorbing compounds, but the photon flux absorbed by S is lower in the mixture. Interestingly, in a solution containing S and R as radiation-absorbing species, at a given wavelength λ the ratio of the respective absorbances would be equal to the ratio of the absorbed spectral photon flux densities: AS(
λ
) [AR(λ
)]−1 = pa,S(λ
) [pa,R(λ
)]−1 (Braslavsky, 2007). It is also AS(λ
) [Atot(λ
)]−1 = pa,S(λ
) [pa,tot(λ
)]−1, where Atot(λ
) =AS(λ
) + AR(λ
). Given these premises, the photon flux absorbed by AQ2S in the presence of nitrite (PaAQ2S) can be obtained as follows:]} [ ) ( ] 2 [ ) ( { ) ( 2 2 2 − ⋅ + ⋅ ⋅ =b AQ S − NO Atot λ εAQ S λ εNO λ (1)
] 10 1 [ ) ( ) ( ( ) , λ
λ
λ
Atot tot a p p = ° ⋅ − − (2) 1 2 2 2 , 2 , ( ) ( ) ( ) [ 2 ] { ( ) [ 2 ] ( ) [ ]} 2 − − ⋅ + ⋅ ⋅ ⋅ ⋅ = p AQ S AQ S − NO paAQ S λ atot λ εAQ S λ εAQ S λ εNO λ (3)λ
λ
λ d p P aAQ S S AQ a =∫
, 2 ( ) 2 (4)where p°(
λ
) is the lamp photon flux reaching the solution,ε
AQ2S andε
NO2− the molar absorption coefficients of AQ2S and nitrite, respectively, and b = 0.4 cm the optical path length of the irradiated solution. PaAQ2S decreases with increasing nitrite concentration (see Figure A-SM in the Supplementary Material, hereafter SM). In the case of 0.1 mM AQ2S one gets the following linear trend: PaAQ2S [EinsteinL−1 s−1]=(2.01±0.01)⋅10−6 −(1.62±0.04)⋅10−5[NO2−].Laser flash photolysis experiments. Laser flash photolysis (LFP) experiments were performed by using the third harmonic (λexc = 355 nm) of a Quanta Ray GCR 130-01 Nd:YAG laser system instrument, used in a right-angle geometry with respect to the monitoring light beam. The single pulses were ca. 9 ns in duration, with an energy of 65 mJ/pulse. Individual cuvette samples (3 mL volume) were used for a maximum of two consecutive laser shots. The transient absorbance at the pre-selected wavelength (λdet) was monitored by a detection system consisting of a pulsed xenon lamp (150 W), monochromator and a photomultiplier (1P28). A spectrometer control unit was used for synchronising the pulsed light source and programmable shutters with the laser output. The signal from the photomultiplier was digitised by a programmable digital oscilloscope (HP54522A). A 32 bits RISC-processor kinetic spectrometer workstation was used to analyse the digitised signal.
The second-order rate constant with nitrite of 3AQ2S* and related exciplexes with water was determined from the regression lines of the absorbance logarithm decay against [NO2−]. All experiments were performed at ambient temperature (295±2 K) in aerated solution. pH was adjusted at 8.0 with NaOH.
Three transient species were identified upon laser excitation of AQ2S as reported previously (Loeff et al., 1983; Maddigapu et al., 2010). The first one, monitored at 380 nm was identified with 3
AQ2S*. It quickly decays (kdecay3AQ2S* ~ 6.8⋅10
7
s−1) leading to the formation of two exciplexes: B with a slow decay (kdecayB ~ 2.7⋅10
4
s−1) and C (kdecayC ~ 2.8⋅10
6
s−1), monitored at 520 and 600 nm respectively.
Results and Discussion
AQ2S-enhanced phenol photonitration
Figure 2 reports the time evolution of 2-nitrophenol (2NP, 2a) and 4-nitrophenol (4NP, 2b) upon UVA irradiation of 1 mM phenol, 1-4 mM NaNO2 and 0.1 mM AQ2S. AQ2S considerably enhances the photonitration of phenol in the presence of nitrite, because no nitrophenols were detected in its absence. Figure 3 shows the corresponding initial formation rates of 2NP and 4NP, which are directly proportional to the concentration of nitrite. Negligible nitrophenol formation rates were observed without AQ2S. One gets the following linear dependence of Rate2NP and Rate4NP vs. [NO2−]: (2.54 0.08) 10 [ 2] 6 2 − − ⋅ ± = NO Rate NP ; Rate4NP =(1.65±0.07)⋅10−6[NO2−]; ] [ 10 ) 11 . 0 19 . 4 ( 6 2 4 2 − − ⋅ ± = + =Rate Rate NO RateNP NP NP .
The formation of nitrophenols in aqueous solution is initiated by the reaction of phenol with
•NO
2, which is in competition with the hydrolysis of nitrogen dioxide (Machado and Boule, 1995; Dzengel et al., 1999):
2 •NO2 N2O4(+ H2O)→ NO2− + NO3− + 2 H+ (5)
In the presence of 1 mM phenol, practically all •NO2 would react with phenol to give the nitrophenols (Chiron et al., 2007b). Under such circumstances, RateNP would be a measure of the generation rate of •NO2 in the studied system. The quantum yield of nitrophenol generation by irradiated AQ2S is
Φ
NPAQ2S = RateNP (PaAQ2S)−1, where PaAQ2S is the photon flux absorbed by AQ2S. As already reported, in the presence of competition for irradiance by nitrite it is] [ 10 ) 04 . 0 62 . 1 ( 10 ) 01 . 0 01 . 2 ( 6 5 2 2 = ± ⋅ − − ± ⋅ − − NO PaAQ S . Considering that ] [ 10 ) 11 . 0 19 . 4 ( 2 6 − − ⋅ ± = NO
RateNP , one gets the following trend of
Φ
NPAQ2S vs. [NO2−]: ] [ 10 ) 04 . 0 62 . 1 ( 10 ) 01 . 0 01 . 2 ( ] [ 10 ) 11 . 0 19 . 4 ( 2 5 6 2 6 2 − − − − − ⋅ ± − ⋅ ± ⋅ ± = Φ NO NO S AQ NP (6)
In the presence of 1 mM phenol, under the hypotheses that practically all •NO2 reacts with phenol and that the nitrophenols (2NP and 4NP) are formed with unity yield by reaction of phenol with one
•NO
2 molecule (Chiron et al., 2007b),
Φ
NPAQ2S would be a measure of the quantum yield of •NO2 photoproduction by radiation-excited AQ2S: AQNP2S AQNO2S2 • Φ = Φ (otherwise it would be S AQ NO S AQ NP 2 2 2 • Φ <
Φ ). Interestingly, a sub-mM [NO2−] would be sufficient to have (1.62
±
0.04)⋅
10−5 [NO2−] «(2.01±
0.01)⋅
10−6. In surface waters [NO2−] has often sub-µM levels, thus equation (6) would be modified as follows:] [ ) 06 . 0 08 . 2 ( 2 2 2 − ± ≈ Φ• NO S AQ NO (7)
Laser flash photolysis experiments
Figure 4 shows the trend of the pseudo-first order decay constant of 3AQ2S* vs. [NO2−]. The linear fit of the experimental data gives the second-order rate constant between 3AQ2S* and NO2−,
−
2 * 3AQ2S ,NO
k = (2.35±0.25)⋅109 M−1 s−1 (µ±σ). This value compares well with Loeff et al. (1983), who found 3⋅109 M−1 s−1 at pH ~ 6.0.
At 520 nm the absorbance decay was fitted with a double-exponential plot, indicating the presence of two species: on the basis of literature data, the first was attributed to the exciplex B between 3AQ2S* and water (Maddigapu et al., 2010a), the second to the AQ2S radical anion (AQ2S−●) (Hulme et al., 1972). AQ2S−● is formed by electron transfer between 3AQ2S* and NO2−:
3
AQ2S* + NO2− → AQ2S−● + ●NO2 (8)
Figure 5a shows the trend vs. [NO2−] of the maximum absorbance reached by B and AQ2S−● at 520 nm. The absorbance of B decreased from 0.081 in water to 0.020 with 5 mM NO2−. The absorbance of AQ2S−● increased quickly and reached a plateau around 0.15 at 2 mM NO2−.
Figure 5b shows the pseudo-first order decay constants of B and AQ2S−● as function of [NO2−]. In the case of B there is an evident quenching by NO2− and it is possible to calculate the second-order rate constant, −
2
,NO
B
k = (1.03±0.04)⋅107 M−1 s−1. This is interesting because B usually shows poor reactivity with dissolved species (Maddigapu et al., 2010). The pseudo-first order decay constant of AQ2S−● (kAQ2S−•) is close to 5.8⋅105 s−1. As expected, no reactivity was found with NO2−.
Finally, the reactivity between the second exciplex (C) and nitrite was investigated at 600 nm. The maximum absorbance of C decreased from 0.14 in water to 0.06 with 5 mM nitrite, but no reaction between C and NO2− could be detected. Nitrite inhibits the formation of C, rather than enhancing its decay, because reaction (8) consumes 3AQ2S* that is no longer able to yield C via reaction with water.
Note that 3AQ2S* reacts with nitrite faster than B, but it is also much more unstable: therefore, production of •NO2 by irradiated AQ2S involves 3AQ2S* in the ns scale and B in the µs one after photon absorption. Nitrite at mM levels is not able to totally quench 3AQ2S* (one needs some 3 mM NO2− to get 2 *
3AQ S
decay
k twice higher than in water, see Figure 4). Therefore, in the presence of sub-mM NO2− there would be limited quenching of 3AQ2S*, which allows the formation of B and its further reaction with nitrite.
Environmental significance
The photogeneration of •NO2 in surface waters can take place upon nitrate photolysis and nitrite photooxidation by •OH, CO3−• (Mack and Bolton, 1999; Buxton et al., 1988; Neta et al., 1988), and probably also 3CDOM*.
NO3− + hν + H+→•OH + •NO2 [Φ9 = 0.01] (9) NO2− + •OH →•NO2 + OH− [k10 = 1.0×1010 M−1 s−1] (10) NO2− + CO3−•→•NO2 + CO32− [k11 = 4.0×105 M−1 s−1] (11)
NO2− + 3CDOM* →•NO2 + CDOM−• (12)
As far as reaction (12) is concerned, it is made the hypothesis that the quantum yield of •NO2 photoproduction by CDOM is described by equation (7). It is possible to model the photoproduction and the reactivity of •OH, CO3−• and 3CDOM* in surface waters as a function of the water chemical composition and column depth d (Maddigapu et al., in press). The same models, which are described in the SM, can be adapted to the assessment of the formation rate of •NO2 via reactions (9-12). The corresponding equations are also reported in the SM.
In the case of nitrate photolysis (reaction (9)) it would be R•OHNO3− = R•NO2NO3−. Interestingly, the formation rate of •OH/•NO2 is influenced by the pH and the inorganic carbon content of the solution (Vione et al., 2009). About reaction (10), nitrite is usually a secondary •OH scavenger in surface waters compared to DOM or carbonate/bicarbonate. The same applies to NO2− and CO3−• in equation (11), the main CO3−• scavenger being DOM (Maddigapu et al., in press). Concerning reaction (12), it is R•NO2CDOM =
Φ
•NO2CDOM PaCDOM, whereΦ
•NO2CDOM is given by equation (7) and PaCDOM is the sunlight photon flux absorbed by CDOM.Assume R•NO2NO3−, R•NO2NO2−,•OH, R•NO2NO2−,CO3−• and R•NO2CDOM as the formation rates of •NO2 because of reactions (9), (10), (11) and (12), respectively. Model results yield negligible R•NO2NO2−,CO3−• under conditions that are significant for surface waters.
Figure 6a reports R•NO2NO3−, R•NO2NO2−,•OH and R•NO2CDOM, calculated according to the photochemical models described in SM, in a well-mixed water body containing 1 mM HCO3−, 10 µM CO32−, 4 µM NO3− and 0.3 µM NO2−. The rates are plotted as a function of NPOC (Non-Purgeable Organic Carbon, which is a measure of the organic matter content) and of the water column depth d. As reported in the SM, the water absorption spectrum was modelled based on the NPOC value. The irradiation conditions correspond to sunlight with 22 W m−2 UV irradiance, which can be observed in a fair-weather 15 July at 45°N latitude, at 10 am or 2 pm (for the spectrum of sunlight see Figure B-SM). It can be seen that all the rates decrease with d; this is reasonable considering that the photochemical reactions are most important in shallow water bodies. Both R•NO2NO3− and R•NO2NO2−,•OH decrease with increasing NPOC: dissolved organic compounds absorb radiation, inhibiting the photolysis of nitrate, and consume •OH that is thus prevented to react with nitrite. On the contrary, R•NO2CDOM increases with increasing NPOC. This is
reasonable considering the proportionality between R•NO2CDOM and PaCDOM, the latter increasing with the organic matter content. Interestingly, if d > 1 m and NPOC > 5 mg C L−1, reaction (12) between nitrite and 3CDOM* would become the main source of •NO2.
Figure 6b reports R•NO2tot = R•NO2NO3− + R•NO2NO2−,•OH + R•NO2NO2−,CO3−• + R•NO2CDOM as a function of d and NPOC, for the same model water body assumed in Figure 6a. R•NO2tot decreases with increasing NPOC and d. Moreover, the residual R•NO2tot at elevated NPOC is mainly accounted for by R•NO2CDOM. It can be inferred that reaction (12) (nitrite + 3CDOM*) could play an important role as •NO2 source in water bodies with an elevated [NO2−] [NO3−]−1 ratio (otherwise the photolysis of nitrate, reaction (9), could prevail as the source of •NO2), for elevated values of d and NPOC. The latter conditions are not the most favourable for R•NO2tot to be elevated, but the contribution of 3CDOM* would prevent R•NO2tot from being still lower. Also note that dissolved organic matter would be a minor sink of •NO2 at the NPOC values that can be found in most water bodies: hydrolysis (reaction (5)) would prevail in the vast majority of cases (Chiron et al., 2007b).
Conclusions
Here it is shown that UVA-irradiated AQ2S is able to oxidise nitrite to •NO2. Phenol nitration was adopted as •NO2 probe, giving a quantum yield (2.08 0.06)[ 2]
2 2 − ± = Φ• NO S AQ
NO for sub-mM nitrite
under the hypothesis that nitrophenols (2NP and 4NP) are formed with unity yield from phenol and one •NO2 molecule. Both 3AQ2S* and its 520-nm absorbing exciplex with water are involved in the process, at different time scales (ns and µs, respectively, after photon absorption).
AQ2S was adopted here as a proxy of CDOM, an important fraction of which is made up by quinones (Cory et al., 2005). Under the hypothesis that AQNO2S
2
•
Φ is representative of the behaviour of CDOM, the oxidation of nitrite to •NO2 by 3CDOM* would be an important •NO2 source in water bodies with high [NO2−] to [NO3−] ratio, for elevated values of column depth and NPOC.
Acknowledgements
DV, VM and CM acknowledge financial support by PNRA-Progetto Antartide. The work of PRM in Torino was supported by a Marie Curie International Incoming Fellowship (IIF), under the FP7-PEOPLE programme (contract n° PIIF-GA-2008-219350, project PHOTONIT).
References
Agarwal, H. C., Singh, D. K., Sharma, V. B., 1994. Fate of parathion in soil under subtropical field conditions. J. Environ. Sci. Heal. B29, 189-194.
Braslavsky, S.E., 2007. Glossary of terms used in photochemistry, 3rd edition. Pure Appl. Chem. 79, 293-465.
Buxton, G. V., Greenstock, C. L., Helman, W. P., Ross, A. B., 1988. Critical review of rate constants for reactions of hydrated electrons, hydrogen atoms and hydroxyl radicals (•OH/•O−) in aqueous solution. J. Phys. Chem. Ref. Data 17, 1027-1284.
Canonica, S., Kohn, T., Mac, M., Real, F. J., Wirz, J., von Gunten, U., 2005. Photosensitizer method to determine rate constants for the reaction of carbonate radical with organic compounds. Environ. Sci. Technol. 39, 9182-9188.
Canonica, S., Hellrung, B., Muller, P., Wirz, J., 2006. Aqueous oxidation of phenylurea herbicides by triplet aromatic ketones. Environ. Sci. Technol. 2006, 40, 6636-6641.
Chiron, S., Barbati, S., De Méo, M., Botta, A., 2007a. In vitro synthesis of 1,N6 -etheno-2’-deoxyadenosine and 1,N2-etheno-2’-deoxyguanosine by 2,4-dinitrophenol and 1,3-dinitropyrene in presence of a bacterial nitroreductase. Environ. Toxicol. 22, 222-227.
Chiron, S., Minero, C., Vione, D., 2007b. Occurrence of 2,4-dichlorophenol and of 2,4-dichloro-6-nitrophenol in the Rhône river delta (Southern France). Environ. Sci. Technol. 41, 3127-3133. Chiron, S., Comoretto, L., Rinaldi, E., Maurino, V., Minero, C., Vione, D., 2009a. Pesticide by-products in the Rhône delta (Southern France). The case of 4-chloro-2-methylphenol and of its nitroderivative. Chemosphere 74, 599-604.
Cory, R. M., McKnight, D. M., 2005. Fluorescence spectroscopy reveals ubiquitous presence of oxidized and reduced quinones in dissolved organic matter. Environ. Sci. Technol. 39, 8142-8149.
Dzengel, J., Theurich, J., Bahnemann, D. W., 1999. Formation of nitroaromatic compounds in advanced oxidation processes: photolysis versus photocatalysis. Environ. Sci. Technol. 33, 294-300.
Halladja, S., Ter Halle, A., Aguer, J. P., Boulkamh, A., Richard, C., 2007. Inhihition of humic substances mediated photooxygenation of furfuryl alcohol by 2,4,6-trimethylphenol. Evidence for reactivity of the phenol with humic triplet excited states. Environ. Sci. Technol. 41, 6066-6073.
Howe, G. E., Marking, L. L., Bills, T. D., Rach, J. J., Mayer, F. L., 1994. Effects of water temperature and pH on toxicity of terbufos, trichlorfon, 4-nitrophenol and 2,4-dinitrophenol to the amphipod Gammarus pseudolimnaeus and rainbow trout (Onchorhynchus mykiss). Environ. Toxicol. Chem. 13, 51-66.
Hulme, B. E., Land, E. J., Phillips, G. O., 1972. Pulse radiolysis of 9,10-anthraquinones. J. Chem. Soc. Faraday Trans. 1. 68, 1992-2002.
Loeff, I., Treinin, A., Linschitz, H., 1983. Photochemistry of 9,10-anthraquinone-2-sulfonate in solution. 1. Intermediates and mechanism, J. Phys. Chem 87, 2536-2544.
Machado, F., Boule, P., 1995. Photonitration and photonitrosation of phenolic derivatives induced in aqueous solution by excitation of nitrite and nitrate ions. J. Photochem. Photobiol. A: Chem. 86, 73-80.
Mack, J., Bolton, J. R., 1999. Photochemistry of nitrite and nitrate in aqueous solution: A review. J. Photochem. Photobiol. A: Chem. 128, 1-13.
Maddigapu, P. R., Bedini, A., Minero, C., Maurino, V., Vione, D., Brigante, M., Mailhot, G., Sarakha, M., 2010. The pH-dependent photochemistry of anthraquinone-2-sulfonate. Photochem. Photobiol. Sci. 9, 323-330.
Maddigapu, P. R., Minella, M., Vione, D., Maurino, V., Minero, C., in press. Modeling phototransformation reactions in surface water bodies: 2,4-Dichloro-6-nitrophenol as a case study. Environ. Sci. Technol., DOI: 10.1021/es102458n.
Maurino, V., Borghesi, D., Vione, D., Minero, C., 2008. Transformation of phenolic compounds upon UVA irradiation of anthraquinone-2-sulfonate. Photochem. Photobiol. Sci. 7, 321-327. Neta, P., Huie, R. E., Ross, A. B., 1988. Rate constants for reactions of inorganic radicals in
aqueous solution. J. Phys. Chem. Ref. Data 17, 1027-1230.
Shea, P. J., Weber, J. B., Overcash, M. R., 1983. Biological activities of 2,4-dinitrophenol in plant-soil systems. Residue Rev. 87, 1-41.
Umamaheswari, A., Venkateswarlu, K., 2004. Impact of nitrophenols on the photosynthetic electron transport chain and ATP content in Nostoc muscorum and Chlorella vulgaris. Ecotox. Environ. Safe. 58, 256-259.
Vione, D., Maurino, V., Minero, C., Pelizzetti, E., 2002. Phenol photonitration. Ann. Chim. (Rome) 92, 919-929.
Vione, D., Khanra, S., Cucu Man, S., Maddigapu, P. R., Das, R., Arsene, C., Olariu, R. I., Maurino, V., Minero, C., 2009. Inhibition vs. enhancement of the nitrate-induced phototransformation of organic substrates by the •OH scavengers bicarbonate and carbonate. Wat. Res. 43, 4718-4728.
Wardman, P., 1989. Reduction potentials of one-electron couples involving free radicals in aqueous solution. J. Phys. Chem. Ref. Data 18, 1637-1755.
Figure 1. Molar absorption coefficients of AQ2S and nitrite (the latter multiplied by 103). Emission spectrum of the adopted UVA lamp.
Figure 2. Time evolution of 2NP (2a) and of 4NP (2b) upon UVA irradiation of 0.1 mM AQ2S in
aerated solution at pH 8.0, in the presence of 1 mM phenol and variable concentration values of nitrite (reported near each curve).
Figure 3. Initial formation rates of 2NP and 4NP upon UVA irradiation of 0.1 mM AQ2S with 1
mM phenol, as a function of nitrite concentration. Error bars derived at σ level from the fitting of the experimental data.
Figure 4. Pseudo-first order decay constant (s-1) of 3AQ2S*, followed at 380 nm after laser pulse excitation (65mJ, 355nm) of AQ2S in the presence of different nitrite concentrations. The experiments were carried out in aerated solution at 295 ± 2 K and pH 8.0. Error bars derived at 3σ level from the monoexponential fitting of the experimental data.
Figure 5. a) Absorbance at 520 nm of B and AQ2S−● with different [NO2−].
b) Pseudo-first order decay constants (s−1) of B and AQ2S−● as function of [NO2−]. The experiments were carried out in aerated solution at 295 ± 2 K and pH 8.0 and were followed at 520 nm. Error bars derived at 3σ level from the fitting of the experimental data.
Figure 6. a) Modelled formation rate of •NO2 upon nitrate photolysis (RNO2_NO3−), nitrite oxidation by •OH (RNO2_NO2−_•OH) and nitrite oxidation by 3CDOM* (RNO2_DOM), as a function of the column depth d and of the dissolved organic carbon (DOC) content, measured as NPOC, of a hypothetical water body. The water-body photochemistry was modelled as described in the SM. Irradiation conditions on top of the water surface correspond to a 22 W m−2 sunlight UV irradiance (see Figure B-SM).
b) Total formation rate of •NO2 (RNO2tot = RNO2_NO3− + RNO2_NO2−_OH• + RNO2_DOM), as a function of d and NPOC.
